How to Grow Harrow Diamond
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Harrow Diamond
Solanum lycopersicum 'Harrow Diamond'
vegetableHarrow Diamond is a hybrid determinate tomato variety developed by Agriculture and Agri-Food Canada, bred specifically for disease resistance and reliability. It produces medium-sized, round red fruits with excellent flavor and crack resistance, making it ideal for fresh market and home gardens. This variety is known for its strong plant vigor and consistent yields even in challenging growing conditions.
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Example Harrow Diamond timeline · Pittsburgh, PA (Zone 6b)
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Plant Harrow Diamond
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Harrow Diamond
Around Jun 26≈ 70 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Harrow Diamond dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 4-9, with excellent cold-season performance in zone 3-4
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Seedling
2-3 weeksTiny plants with cotyledons (seed leaves) emerging, followed by first true leaves
Keep soil moist but not waterlogged. Provide bright light (14-16 hours) to prevent leggy growth. Maintain temperatures of 70-75°F.
Vegetative Growth
4-6 weeks indoors; 1-2 weeks after transplanting outdoorsPlant develops robust stem and multiple sets of true leaves; leaf canopy becomes fuller
Transplant seedlings when 2-3 true leaves appear. Harden off before field planting. Begin low nitrogen feeding to encourage strong stems. Support early with stakes.
Flowering
3-4 weeksYellow flower clusters appear in axils between stems; flowers open and self-pollinate
Maintain consistent watering; irregular water causes blossom end rot and cracking. Support developing flower clusters with twine or cages. Ensure adequate pollination through air circulation or gentle shaking.
Fruit Development & Growth
4-6 weeksGreen fruits form and enlarge from marble-size to full diameter (2-3 inches); plant becomes heavily laden
Prune selectively to improve air flow and fruit ripening; remove lower leaves after fruit set. Maintain even moisture. Provide consistent fertilization with balanced nutrients. Watch for disease pressure.
Ripening & Harvest
2-3 weeks per fruit cluster; continuous until frostFruits transition from green to full red color; they soften slightly and develop characteristic tomato aroma
Reduce water slightly to concentrate sugars (but don't allow drought stress). Continue removing lower foliage for air circulation. Harvest when fully colored for best flavor, or at first blush for later ripening.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Hand-pick large worms; use Bt (Bacillus thuringiensis) spray for larvae; encourage beneficial wasps
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Use yellow sticky traps; spray neem oil or insecticidal soap on leaf undersides; encourage ladybugs
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Spray strong water stream to dislodge; use neem oil or insecticidal soap; introduce natural predators
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Increase humidity; spray miticide or neem oil; remove heavily infested leaves
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Remove lower infected leaves; improve air circulation; mulch to prevent soil splash; use copper fungicide if needed
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Remove infected leaves promptly; water only at soil level; apply chlorothalonil or fixed copper fungicide
Uses
Fresh eating and slicing
CulinaryHarrow Diamond's medium size and excellent flavor make it ideal for fresh slicing in salads, sandwiches, and on burgers. The natural sweetness and crack resistance ensure consistent, juicy results without splitting. [source]
Sauce and preserves
CulinaryWith good flesh density and balanced acidity, these tomatoes work well for making homemade pasta sauce, salsa, and tomato paste. The reliable yields allow for larger-batch processing. [source]
Cardiovascular health
MedicinalTomatoes are rich in lycopene, an antioxidant linked to heart health and cancer prevention. Regular consumption contributes to a heart-healthy diet. [source]
Gardening reliability
HouseholdHarrow Diamond's disease resistance (notably to leaf spot and blight) and cold tolerance make it a dependable choice for northern gardens and challenging seasons, requiring less fungicide intervention. [source]
Pollinator attraction
WildlifeThe abundant yellow flowers attract bees and beneficial insects to the garden, supporting broader pollination and ecosystem health. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Pick fruits when fully red (vine-ripened) for maximum flavor and sweetness, or at first blush if you prefer earlier harvest. Gently twist and pull to avoid damaging the vine. Harrow Diamond fruits store well on the counter; do not refrigerate as this diminishes flavor. Continue harvesting until first frost.
Fun Facts
- 🌱 Harrow Diamond was developed by Agriculture and Agri-Food Canada at the Harrow Research Station in Ontario, earning its name from this breeding program and its roughly diamond-shaped fruit profile.
- 🌱 This variety is particularly prized in regions with short growing seasons and cool nights because it sets fruit reliably even under suboptimal temperature conditions that would cause flower drop in other varieties.
- 🌱 The 'crack resistance' in Harrow Diamond refers to its ability to resist skin splitting during sudden water surges or rainfall, a trait achieved through selective breeding for firmer fruit skin and balanced cell-wall structure.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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